Analysis of soil temperature and moisture characteristics of artificial grasslands with different underlying surfaces in southeast Tibet

To explore soil temperature and moisture characteristics of artificial grasslands on different underlying surfaces in Southeast Tibet, temperature and moisture data at a depth of 10 cm were collected from Mount Lawu, Mangkang County, Tibet, between November 2015 and December 2017. Data of three underlying surfaces for artificial grasslands, namely vegetation mulching (vegetation area), gravel + vegetation mulching (gravel area), and no mulching (bare land), were collected and compared. The results are as follows. 1) The trend of soil temperature at a depth of 10 cm was sinusoidal on all three underlying surfaces, which is consistent with the trend of solar radiation. The maximum and minimum values were recorded in July and January, respectively. Annual variation in soil temperature was the greatest (25.46 and 23.38 ℃ , respectively) in gravel area and the smallest (17.17 and 16.65 ℃, respectively) in vegetation area. The trend of daily variation in soil temperature was sinusoidal in gravel area, and soil temperature in bare land and vegetation area fluctuated slightly from 11:00 to 13:00. 2) On the seasonal scale, soil moisture was mainly affected by annual variation in precipitation, and it fluctuated periodically, assuming a W-shaped trend. On the daily scale, peak soil moisture values in summer and autumn were recorded in the midnight and evening, respectively, in gravel area, but there were no obvious daily changes in soil moisture in vegetation area and bare land. 3) In non-vegetative growth season (early November to late April), unstable, daily freezing and thawing were observed in gravel area, while the freezing and thawing process was relatively simple in vegetation area and bare land. In vegetative growth season (mid-May to mid-October), soil temperature and moisture were significantly higher (P < 0.05),and the hydrothermal conditions were better in gravel area than in vegetation area. These results indicate that gravel + vegetation mulching is an ideal underlying surface to regulate soil moisture and temperature conditions in artificial grasslands. These data can provide theoretical basis for grassland restoration.